Method for adding a large quantity of manganese alloy during the production of steel through cored wires

ABSTRACT

A method for adding a large quantity of manganese alloy during the production of steel through cored wires is described. In various implementations, manganese alloy is enclosed within a cored wire. The wire is then added to a ladle containing molten primary steel. The wire sinks into the molten primary steel, and the outer encasing melts, thereby exposing the manganese alloy. The manganese alloy itself then melts. By having the manganese alloy encased in steel prior to being added to the molten primary steel, toxic gases and particles from the manganese are trapped within the molten steel. Furthermore, the outer encasing prevents manganese dust from escaping into the environment during transportation, which occurs when unprotected lumps of material are used. This helps prevent humans from being unnecessarily exposed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Argentine patent applicationP050100832, filed Mar. 4, 2005, in the Instituto Nacional de laPropiedad Industrial, which is incorporated by reference herein in itsentirety.

TECHNICAL FIELD

The invention relates generally to the steel manufacturing methods and,more specifically, to a method for adding a large quantity of manganesealloy during the production of primary steel through cored wires.

BACKGROUND

When steel manufacturers produce steel, they often add other materialsto achieve certain desirable characteristics. When manufacturingstructural and specialty steel, they add manganese alloys (High, Mediumand Low Carbon Ferro Manganese, Normal and Low Carbon Silico Manganese)with ranges of manganese content between 50% and 90%. Manganese alloysare also used as deoxidizers and for alloy making. The actual methodused in most steel mills in the treatment of primary steel involvesadding the manganese alloy in the form of lumps of varying sizes. Thelumps are transported in trucks to the steel mills, discharged andstored in warehouses. These lumps are subsequently transported to hopperaddition systems using methods such as conveyor belts or elevators. Thesteel to which the manganese alloy is to be added (hereinafter “primarysteel”) is then chemically analyzed to determine how much of themanganese alloy should be added. After that determination is made, thenecessary quantities of the alloy are aggregated in a casting ladle.Subsequently, molten primary steel is bled into the casting ladle. Thisis the point of application of the alloy to the primary steel, and isindependent of the type of process used to obtain the primary steel andof the final treatment of the steel.

A problem with adding manganese to the primary steel in this manner isthat it generates a significant volume of manganese dust (duringtransportation), and a significant volume of manganese gasses at thesurface of the molten primary steel. Recent studies conducted in theUnited States of America have indicated that the exposure to manganesegasses can cause a disease called Manganism, which has symptoms that aresimilar to those of Parkinson's disease. Thus, it can be seen that thereis a need for a new method for adding manganese alloy to steel thatreduces the emission of gasses.

SUMMARY

In accordance with the foregoing, a method for adding a manganese alloyto primary steel is provided. According to an embodiment of theinvention, the method includes enclosing the manganese alloy within acored wire, and introducing the cored wire into molten primary steel.The enclosing step may include bending a strip into a generally circularshape around the manganese alloy so as to create a continuous tubularpackage having a diameter greater than 21 millimeters, and may alsoinclude forming a lock seal with the outer casing. The outer casing maybe made of a variety of materials, including steel.

In one embodiment, the manganese alloy is crushed into particles, whichmay each have a diameter of about 5 millimeters or less.

The introducing step may include the step of unrolling the wire from acoil, transporting the unrolled wire to the molten primary steel, andpermitting the unrolled wire to drop into the molten primary steel. Thetransporting step may include feeding the unrolled wire through afeeding machine that has rollers that carry the unrolled wire to a ladlethat contains the molten primary steel.

The introducing step may also include determining the length of wire toadd to the molten primary steel, unrolling the wire to the extent of thedetermined length, and permitting the unrolled wire to drop into themolten steel.

In another embodiment of the invention, a method for adding manganese toprimary steel includes the steps of crushing a manganese alloy intoparticles, putting the particles into a sheet of material (which may bea strip of steel), bending the sheet of material around the particles tocreate a cored wire (which may have a diameter greater than 21millimeters), heating primary steel until it is in a molten state,introducing a length of the wire into the molten primary steel, andmelting the sheet of material within the molten primary steel. Themethod may further include calculating the amount of the manganese alloythat is to be added to the molten primary steel, converting thecalculated amount into the length, and programming the length into acontrol system of a feeder. The wire may be stored in the form of acoil, and introduced into the molten primary steel by adding the wire toa ladle into which the molten primary steel is being bled. The methodmay further include forming a lock seal around the particles with thestrip of material.

In yet another embodiment of the invention, a method for manufacturingsteel includes melting a raw material into molten primary steel,bleeding the molten primary steel into a ladle, crushing a manganesealloy into particles, surrounding the particles with a protective jacket(which may be made of steel) to create a cored wire, and determining theamount of the alloy that needs to be added to the molten primary steel.Then, based on the determined amount, the length of the cored wire thatis to be added to the molten primary steel is calculated, and thecalculated length of the cored wire is placed into the ladle.

The method may also include enclosing the particles within theprotective jacket, and melting the protective jacket within the moltensteel, thereby exposing the particles to the molten primary steel.

To place the cored wire into the ladle according to one embodiment, thelength is programmed into a control system of a feeder, and the coredwire is introduced into the feeder.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 (FIG. 1) shows a cross-sectional view of a cored wire accordingto an embodiment of the invention.

FIG. 2 shows how the cored wire is added to a ladle with primary steelaccording to an embodiment of the invention.

FIGS. 3A-3C show various ways in which the cored wired may be stored invarious embodiments of the invention.

DESCRIPTION

The invention is generally directed to a method for adding a largequantity of manganese alloy during the production of primary steel (theapplication point) through cored wires. In various embodiments of theinvention, manganese alloy is rolled into a wire having an outerencasing that has a higher resistance to heat than the manganese alloy.The wire is then added to a ladle containing molten, primary steel. Thewire sinks into the primary steel, and the outer encasing melts, therebyexposing the manganese alloy. The manganese alloy itself then melts. Byhaving the manganese alloy encased in steel prior to being added to themolten primary steel, toxic gases and particles from the manganese aretrapped within the molten primary steel. This helps prevent humans frombeing unnecessarily exposed.

To create primary steel (to which the cored wire is eventually added), araw material, such as iron ore or metallurgic coke, is introduced intothe upper portion or “swallower” of a blast furnace. From this process,liquid pig iron is formed. The liquid pig iron is then evacuated fromthe blast furnace through casting channels located in the lower part ofthe blast furnace. The liquid pig iron is then transported to aconverter (in a wheeled thermos, for example), and charged into theconverter along with steel scrap and fluxes. This mixture is injectedwith oxygen. This primary steel is then produced and is bled into aladle 20, which is shown in FIG. 2.

Another way to create primary steel is as follows. Raw material such assteel scrap, sponge iron, and fluxes is placed into an electric arcfurnace, which has three graphite electrodes and walls made out of arefractory material. An electrical current is then generated, whichproduces an electric arc against the raw material. This process createsprimary steel, which is bled into the ladle 20.

Referring to FIG. 1, the structure of the cored wire according to anembodiment of the invention will now be described. The cored wire,generally labeled 22, is created as follows. A manganese alloy is firstprocured (or manufactured). Suitable manganese alloys include High,Medium and Low Carbon Ferro Manganese, and Normal and Low Carbon SiliconManganese. The percentage of manganese content in the manganese alloymay ranges from about 50% to about 90%, while the carbon content mayrange from about 0.05% to about 7%. The manganese alloy is then crushedinto particles 24 having a diameter of about 5 millimeters or less. Theparticles are loaded into a steel strip 26, in an amount and densitythat is based on such factors as the weight of the alloy content(measured in grams/meter or pounds/foot, for example). The steel strip26 is then rolled into a generally circular shape around the manganesealloy particles 24, and closed by the formation of a lock seal 28. Inone embodiment, the steel strip has a cross-sectional diameter ofgreater than about 21 millimeters.

Referring to FIG. 2, the cored wire 22 is rolled into a coil 12. In oneembodiment, the storage capacity of the coil 12 is between about 1000meters and about 5000 meters of cored wire 22. The coil 12 is thenloaded onto a pallet (e.g., a wooden or steel pallet). The pallet istransported by a forklift which, in one embodiment, has a minimumcapacity of about 2500 kilograms. The coil 12 may then be stored in acovered warehouse. FIGS. 3A-3C show various storage configurations forthe coil 12.

In an embodiment of the invention, the cored wire 22 is added to theprimary steel as it is being bled into the ladle 20. Although there aremany possible ways of accomplishing this, one example process will nowbe described. A steel metallurgist who is familiar with the chemicalcomposition of the primary steel calculates the amount of the manganesealloy that is to be added to the primary steel, and converts this amountinto a length (feet or meters, for example) of the cored wire 22 that isto be added to the ladle 20. This calculation may also be doneautomatically by a control system of the feeding machine 14. An operatorprograms the cored wire length into the control system of the feedingmachine 14. The coil 12 is positioned at one end of the feeding machine14, and unwound. The cored wire 22 is fed through the feeding machine14. The cored wire 22 passes through the rollers 18 of the feedingmachine 14, and into the ladle 20. The cored wire 22 then sinks into themolten primary steel in the ladle 20. As the cored wire 22 sinks, thesteel strip 26 (FIG. 1) temporarily prevents contact between themanganese alloy and the molten primary steel. The heat from the primarysteel then begins to melt the steel strip 26. By the time the steelstrip 26 melts, the cored wire 22 will have reached the deepest portionsof the ladle 20. After the steel strip 26 melts, the manganese alloyitself mixes with the primary steel.

The embodiments of the method described herein confer a number ofadvantages over existing processes. For example, the method permits moreprecise control over how much material gets added to the steel becausethe amount of material in the cored wire is generally homogeneous (interms of weight per meter). Also, because the steel outer strip resists(at least for a short time) heat in the interior of the ladle withoutmelting, the enclosed material will penetrate to the deepest zones ofthe ladle. Thus, the material mixes in at the heart of the liquidprimary steel, which means that the material is used more efficiently,thereby reducing surface reactions and environmental contamination.

It can thus be seen that a new method for adding material to steel hasbeen described. It should be noted that the use of the terms “a” and“an” and “the” and similar referents in the context of describing theinvention (especially in the context of the following claims) are to beconstrued to cover both the singular and the plural, unless otherwiseindicated herein. Recitation of ranges of values herein are merelyintended to serve as a shorthand method of referring individually toeach separate value falling within the range, unless otherwise indicatedherein, and each separate value is incorporated into the specificationas if it were individually recited herein. All methods described hereincan be performed in any suitable order unless otherwise indicated hereinor otherwise clearly contradicted by context. The use of any and allexamples, or exemplary language (e.g., “such as”) provided herein, isintended merely to better illuminate the invention and does not pose alimitation on the scope of the invention unless otherwise claimed. Nolanguage in the specification should be construed as indicating anynon-claimed element as essential to the practice of the invention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention. Itshould be understood that the illustrated embodiments are exemplaryonly, and should not be taken as limiting the scope of the invention.

1. A method for adding a manganese alloy to steel, the method comprising: enclosing the manganese alloy within a cored wire; and introducing the wire into molten primary steel.
 2. The method of claim 1, wherein the enclosing step comprises bending an outer casing into a generally circular shape around the manganese alloy so as to create a continuous tubular package having a diameter greater than 21 millimeters.
 3. The method of claim 1, wherein the application point of the manganese alloy to the molten primary steel is during the tapping of the primary molten steel, and is independent of the process by which the primary steel was obtained.
 4. The method of claim 1, further comprising crushing the manganese alloy into particles.
 5. The method of claim 4, wherein the particles each have a diameter no greater than about 5 millimeters.
 6. The method of claim 1, wherein the outer casing is made of steel.
 7. The method of claim 1, wherein the introducing step comprises unrolling the wire from a coil, transporting the unrolled wire to the molten steel, and permitting the unrolled wire to drop into the molten primary steel.
 8. The method of claim 7, wherein the step of transporting the unrolled wire to the molten steel comprises feeding the unrolled wire through a feeding machine comprising rollers that carry the unrolled wire to a ladle that contains the molten primary steel.
 9. The method of claim 1, wherein the introducing step comprises determining the length of the wire to add to the molten primary steel, unrolling the wire to the extent of the determined length, and permitting the unrolled wire to drop into the molten steel.
 10. A method for adding manganese alloy to steel, the method comprising: crushing a manganese alloy into particles; putting the particles into a sheet of material; bending the sheet of material around the particles to create a cored wire; heating primary steel until it is in a molten state; introducing a length of the wire into the molten primary steel; and melting the sheet of material within the molten primary steel, thereby exposing the particles to the molten primary steel.
 11. The method of claim 10, further comprising calculating the amount of the manganese alloy that is to be added to the molten primary steel, converting the calculated amount into the length, and programming the length into a control system of a feeder.
 12. The method of claim 10, further comprising storing the wire in the form of a coil that is between about 1000 meters and about 5000 meters in length.
 13. The method of claim 10, further comprising forming a lock seal around the particles with the sheet of material.
 14. The method of claim 10, further comprising bleeding the molten primary steel into a ladle, and permitting the wire to drop into the ladle.
 15. The method of claim 10, wherein the wire has a diameter greater than 21 millimeters.
 16. The method of claim 10, wherein the sheet of material is a strip of steel.
 17. A method for adding manganese alloy to steel, the method comprising: melting a raw material into molten primary steel; bleeding the molten primary steel into a ladle; crushing a manganese alloy into particles; surrounding the particles with a protective jacket to create a cored wire; determining the amount of the alloy that needs to be added to the molten primary steel; calculating, based on the determined amount, the length of the cored wire that is to be added to the molten primary steel; and placing calculated length of the cored wire into the ladle.
 18. The method of claim 17, wherein the placing step comprises programming the length into a control system of a feeder, and introducing the cored wire into the feeder.
 19. The method of claim 17, wherein the protective jacket is steel and is configured as a continuous tubular package that contains the manganese alloy particles, and that has a diameter greater than 21 millimeters.
 20. The method of claim 17 enclosing the particles within the protective jacket; and melting the protective jacket within the molten steel, thereby exposing the particles to the molten steel. 